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Topic Review (Newest First)

01-10-2008 10:57 PM

Valiente

To keep the boat level! Why didn't I think of that? (slaps head)

01-10-2008 05:54 PM

sailingdog

But Valiente, Ken Barnes had 14 of them aboard his boat, so I think you really need to have at least seven or eight of them.

Quote:

Originally Posted by Valiente

Will four 8D AGMs do? (about 800 amp/hours).

But thanks for the advice. I don't plan on using it super extensively, but I would have in in "guard" mode on night watches, as I would the AIS. If I were to have it fully on, I would likely be motoring, as you said, in a harbour or a crowded channel. In the English Channel, for instance, I would likely motorsail with the tide (and with the radar on) due to the large number of fast ferries and the large variety of indifferently manned cargo ships.

01-10-2008 05:12 PM

artbyjody

That will be pretty adequate I would think, especially if motor sailing...

01-10-2008 05:07 PM

Valiente

Will four 8D AGMs do? (about 800 amp/hours).

But thanks for the advice. I don't plan on using it super extensively, but I would have in in "guard" mode on night watches, as I would the AIS. If I were to have it fully on, I would likely be motoring, as you said, in a harbour or a crowded channel. In the English Channel, for instance, I would likely motorsail with the tide (and with the radar on) due to the large number of fast ferries and the large variety of indifferently manned cargo ships.

01-09-2008 09:06 PM

artbyjody

Depending on how you configure the Radar to update via your C/E-series display, I know on my 2KW system, I can easily drain a 31D 12V battery within 6 hours, if using the 1 or 3 minute update cycle. It is a power hog. Typically I run it only when in a crowded harbor, or visibility is poor, or when I had a functioning inboard - motoring. If you plan on relying on it more heavily during sailing - you may want to consider upgrading your battery banks so that you can handle more amp hours.

01-09-2008 08:52 PM

sailingdog

just remember...radar can be used for range to an object fairly reliable, but not for bearing to an object.

01-09-2008 08:50 PM

Valiente

The radome size doesn't bother me...the power draw does.

I think my general approach is that I should know my position, and thus don't need so much to be able to "count the pores" as to just have an either/or picture of an outline ahead in the water.

As I stated elsewhere, I hope AIS capability (and the habit of keeping a decent watch) will enhance a 2 KW RADAR to the degree where it's like having a 4 KW, if only because you want to know if you're a mile off the reef, but you want to know if you're ten miles from the supertanker moving at 25 knots. AIS/VHF with an antenna height of 50 feet should give you the latter, and a 2KW RADAR 20 feet off the deck should give you the former.

01-09-2008 08:34 PM

sailingdog

The only major difference is that many of the 4kw units have a narrower beam focus, so will give you higher definition in your radar imaging. These usually have a 24" radome though, so may not be something you're interested in. The 2 kW units have an 18" radome generally.

01-09-2008 08:29 PM

Valiente

Yes, I am coming to realize that learning to read a properly placed 2 KW is probably better than installing a 4 KW on an arch.

The simple fact is that a 2 KW will more than suffice for seeing reefs and other low stationary objects at relatively short distances (under 6 miles), and AIS will help identify moving ships within VHF range. So the "prudent set-up" for the ocean sailor goes from a 4 KW on the mast or arch to a 2 KW on the mast, with an AIS whip on the mast top. Add to that a radar interpretation course, and I believe I'm covered.

4 KW won't tell me much more unless its high enough to significantly see over the horizon, and past the waves.

Somebody correct me if I'm wrong here.

01-09-2008 04:01 PM

Idiens

Quote:

Originally Posted by Valiente

... Perhaps I should just go for a 2 KW higher up (I fly a yankee, so it's not likely to snag), so I can have a decent range and a little bit of a power savings.

Nothing against more power, but there is a limit to its usefulness, as the radar is limited to its horizon and by the height of the target beyond that. So a bouy will vanish over the radar's horizon quite quickly - more power will not help. A ship will be seen at greater range, but it's a bigger reflector - which ensures that more power is not needed.

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